Methyl-4-O-methyl-beta-D-glucopyranuronate ligand of proteins in family: Glucuronoyl_esterase
Stucture
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1 structure: 4G4J: Crystal structure of glucuronoyl esterase S213A mutant from Sporotrichum thermophile in complex with methyl 4-O-methyl-beta-D-glucopyranuronate determined at 2.35 A resolution
The family 15 carbohydrate esterase (CE15) MZ0003, which derives from a marine Arctic metagenome, has a broader substrate scope than other members of this family. Here we report the crystal structure of MZ0003, which reveals that residues comprising the catalytic triad differ from previously-characterized fungal homologs, and resolves three large loop regions that are unique to this bacterial sub-clade. The catalytic triad of the bacterial CE15, which includes Asp 332 as its third member, closely resembles that of family 1 carbohydrate esterases (CE1), despite the overall lower structural similarity with members of this family. Two of the three loop regions form a subdomain that deepens the active site pocket and includes several basic residues that contribute to the high positive charge surrounding the active site. Docking simulations predict specific interactions with the sugar moiety of glucuronic-acid substrates, and with aromatically-substituted derivatives that serve as model compounds for the lignin-carbohydrate complex of plant cell walls. Molecular dynamics simulations indicate considerable flexibility of the sub-domain in the substrate-bound form, suggesting plasticity to accommodate different substrates is possible. The findings from this first reported structure of a bacterial member of the CE15 family provide insight into the basis of its broader substrate specificity.
        
Title: The structure of a novel glucuronoyl esterase from Myceliophthora thermophila gives new insights into its role as a potential biocatalyst. Charavgi MD, Dimarogona M, Topakas E, Christakopoulos P, Chrysina ED Ref: Acta Crystallographica D Biol Crystallogr, 69:63, 2013 : PubMed
The increasing demand for the development of efficient biocatalysts is a consequence of their broad industrial applications. Typical difficulties that are encountered during their exploitation in a variety of processes are interconnected with factors such as temperature, pH, product inhibitors etc. To eliminate these, research has been directed towards the identification of new enzymes that would comply with the required standards. To this end, the recently discovered glucuronoyl esterases (GEs) are an enigmatic family within the carbohydrate esterase (CE) family. Structures of the thermophilic StGE2 esterase from Myceliophthora thermophila (synonym Sporotrichum thermophile), a member of the CE15 family, and its S213A mutant were determined at 1.55 and 1.9A resolution, respectively. The first crystal structure of the S213A mutant in complex with a substrate analogue, methyl 4-O-methyl-beta-D-glucopyranuronate, was determined at 2.35A resolution. All of the three-dimensional protein structures have an alpha/betahydrolase fold with a three-layer alphabetaalpha-sandwich architecture and a Rossmann topology and comprise one molecule per asymmetric unit. These are the first crystal structures of a thermophilic GE both in an unliganded form and bound to a substrate analogue, thus unravelling the organization of the catalytic triad residues and their neighbours lining the active site. The knowledge derived offers novel insights into the key structural elements that drive the hydrolysis of glucuronic acid esters.